Dry cell



Aug. 15, 1939. i P. A. MARsAL DRY CELL Filed March 18, 1936 lNvENToRPAUL A. MARSAL ATTORNEY PatentedAug. 15, 1939 UNITED STATES DRY CELL aulA. Marsal, Lakewood, Ohio, assignor to National Carbon Company, lInc., acorporation of New York Application March 18, 1936, Serial No. 69,503

9 claims.

This invention relates to galvanic cells and, more particularly, toimproved sealing means for so-called dry cells.

It is important to retard or prevent the leakage 5 and evaporation ofmoisture from dry cells, and to permit escape therefrom of gasesgenerated therein. Formerly, a Irelatively thick body of wax compositionwas used to seal the dry cell; and, more recently, a much thinnerclosure, such l as sheet metal, has been used instead of the wax seal.The 'thinner closure usually comprises an v annular disc-like covermember which has-its outer margin permanently and gas-tightly securedtoI the upper end of the zinc container l electrode, and has itsinnermargin gas-tightly vsupported by the central carbon electrode. Thecarbon electrode preferably is sufficiently porous to vent gas generatedinthe cell and is treated with lubricating oil or other suitablecomposition to prevent loss of moisture through its pores. In thesmaller or so-'called Vflashlight size of cell, the top end of thecarbon-electrode carries and contacts with a brass Ycap having a flangeto provide a bearing or support for the inner margin of the cover andfor an electrically non-conductive member which insulates the cover fromthis capand the carbon electrode. Compared with those having wax sealsor closures, the cells provided 'with the thin closures are stronger,more uniform in performance and appearance, and have a 'considerablygreater useful space within the cell for active materiaL-comparingcellsof the same dimensions.

- In some ytypes of cells, such as the metal-sealed cells forflashlightservice, the usefulness of such extra space has been severelylimted'because the flange of the brass cap is exposed inside the cell.

` Under certain conditions the various salts, which partly compose .thecell electrolyte, creep up the 40 inside surface of the zinc can andacross the inner surface of the metal cover, making contact with thecover and the flange of the brass cap and resulting in deterioration anddestruction of the cell. -The creepage of these 4salts is especially ,kharmful at elevated temperatures and humidities,

such as are common in tropical climates. For this reason it has beennecessary to retain as an (Cl. 13G-133) provide a cell in which asubstantial portion of the extra space, made available by the thincover, may be safely used to increase the volume of active material inthe cell; to provide a cell in which metal parts of the closure,especially 5 the gap between such parts, are internally protectedagainst contact with active materialin the cell; to provide a cell whichis more effectively sealed against loss of moisture; and to provide acell which will more successfully withl0 .stand deterioration undervarious conditions of temperature and humidity throughout the world,particularly in or near the tropics and in humid localities. These andother objects and the novel features of this invention will be apparentfrom 15 the following description taken with the accompanying drawing,in which:

Figure 1 is a View, partly in section, illustrating a dry cell embodyingthis invention;

Figures 2 and 3 are sectional views illustrating 20 steps in the processof manufacturing the cell shown in Figure 1;

Figures 4 and 5 are sectional views similar to the top part of Figure 1,illustrating other cells embodying this invention; 25

Figures 6 and '7 are perspective views of the annular bodies of plasticmaterial used in manufacturing thefcells shown in Figures 4 and 5,respectively; v

Figure 8 illustrates a step in another process 30 of manufacturing a,cell embodying this invention; and

Figures 9 and 10 are views illustrating steps in other processes ofmaking dry cells embodying this invention. 35

-According to this invention, an annular body or mass of plastic sealingmaterial, which is moisture repellent and electrically vnon-conductive,is applied to interior surfaces of the cell closure and to interiorportions of the electrode 40 surfaces adjoining the closure, aftertheclosure has been permanently secured to the cell. The composition oftheplastic material is such that, when properly deposited and set insealing position,nit firmly adheres to these internal surfaces 45 andresists any tendency of the electrolyte salts or active material tocreep along or across its surface to short circuit or otherwise damagethat it `internally bridges and 'covers only the 55 joint between theflange of the brass cap and the inner margin of the cover member restingthereon, as Well as the joint between the carbon electrode and the brassca-p; or only the joint between the cover member' and the zinc can. Therelatively thick solid adherent body of plastic material thus protectsand insulates the interior surface of the closure, particularly theadjoining portions of the cover and the brass cap, by preventing accessoi electrolyte thereto; and, said material provides an electrolyteanti-creepage means which also more eiectively seals the cell at thejoints between the closure and the electrodes, preventing loss ormoisture from the cell. By this construction, deterioration of the cellis greatly retarded, and considerably larger 'volume ci active materialmay be safely used in the cell.

The several figures oi the drawing illustrate the invention applied to atypical dry cell of the size used lor flashlight service but theinvention is not limited to this type oi cell. As shown, the cellcomprises a. cylindrical zinc can or container electrode Z; acylindrical carbon electrode C disposed centrally within and spaced fromthe outer electrode Z; a cylindrical body o dcpolarizing and activematerial or Ivi' in which the inner end of the electrode C is embedded;and a bibulous spacing material E between the mix M and the electrode Z.The spacing material E may consist of suitable paste or absorbentmaterial such as paper, and contains a suitable electrolyte such as anaqueous solution of zinc chloride and ammonium chloride. The electrode Cpreferably consists of a solid rod of porous carbon treated with amoisture-'repellent composition, so that gas generated in the cell willvent through this electrode to the atmosphere but substantially nomoisture will escape from the inside of the cell. Otherwise, the partsjust described may be of the usual or any preferred type. An annularcollar K of stiff paperboard or other suitable material is disposed inthe gas space G at a substantial distance above the mix M and is rigidlyheld in place by the frictional engagement of its edges with the insidesurfaces of the electrodes Z and C.

The closure of the cell may comprise a relatively thin annular covermember A and a metal cap B. The cap B may be a cup-shaped mem ber ofbrass or other suitable sheet metal fitting the upper end of theelectrode C, and desirably is provided with an out-turned annular flangeB at its lower edge and a vent, hole B" opposite the top of theelectrode C. The cover A may consist ofrelatively rigid but resilientsheet material such as metal, paperboard, flberboard or molded plasticmaterial; and as shown it consists of thin sheet iron or steel. TheVouter margin of the cover A preferably is permanently and gas-tightlysecured to the upper end of the electrode Z, as by tightly rolling orspinning the margin of the cover A over the circular outwardly-inclinededge of the can Z. thus interlocking adjoining portions of the cover Aand can Z to permanently unite these parts. The inner margin of thecover A is supported by the electrode C, since, it presses firmlyagainst an annular washer W of moistureproof and electrical insulatingmaterial which is carried by the flange B of the cap B that is mountedon the electrode C.

As previously explained,lactive material of the cell often contacts withthe interior surfaces of the closure and the joints between the closureand lthe electrodes, deteriorating or destroying the cell. As shown inFigure 1, this is prevented by applying a body or mass P of suitablematerial to the entire interior surface of the closure and to the joints`between the closure and the electrodes. by melting or `fusing anddepositing said mass into sealing position after the closure has beensecured to the eine can. rUne mass P may consist solely of thermoplasticmaterial which is both moisture-proof and electrically non-conduc tiveand, when set`- adheres' firmly 'to the interior surfaces of the coverand the adjoining interior siufaccs of the electrodes. it will be seenthat the plastic material P bridges the gap between the flange B and thecover A, thereby effectively preventing' access of electrolyte salts tothese parts. In addition, the joint between the cover A and theelectrode Tl and the joint between the cap B and the electrode i; arecompletely and gas-tightly sealed to more eiectively resist loss oi cellmoisture or creepage oi electrolyte salts through or across thesejoints. constitutes the sole means for internally sealing the jointsbetween the cover and the electrodes. and for resisting creepage ofelectrolyte to and across such joints.

Various procedures may be followed in apply ing the unitary body or massP to manufacture an improved cell embodying this invention. As

whereupon the disc D will be guided by the elec? trode C and drop downinto horizontal contact with portions of the interior surface of theclosure. Sufficient heat is then applied to the closure of the cell tomelt the disc D and cause it to flow over and cover the entire interiorsurface of the closure and the joints thereof, to produce the adherentprotective mass P.

In some instances it will be suiilcient to apply yan adherent protectivemass only to the gap between the flange B and the cover A and betweenthe flange B and the electrode C, as shown at P in Figure 4. Here, athermoplastic disc D', as shown in Figure 6, having the same internaldiameter as, but a smaller external diameter than, the disc D, may beused to produce the protective mass P. Similarly, it will be suiicientin some constructions to apply a protective mass only to the jointbetween the cover A and the zinc can Z, as shown at P" in Figure 5. Herea thermoplastic disc D", as shown'in Figure '7, hav ing the sameexternal diameter as, vbut a larger internal diameter than, the disc D,may be used to produce the protective mass P". The masses P and P"prevent, salt creepage to the flange B `and also effectively seal theouter joint of the The mass l? thus cover A free to be lifted off thewasher W, to

and using the discs D and Dl to produce the masses P', P, respectively,except that the Iusing heat may be more'localized in applying theelectrode Z.

'The discs D,D' and D" may consist of any suitable thermoplasticmaterial that may be fused or melted at moderatelyelevated temperaturesvand will readily'solidlfy at ordinary room. temperatures to produce aprotective mass which is adherent after melting and solidiiication, iseiec- 'tricall'y non-conductive, and resistantto moisture and creepageofelectrolyte salt. A thermoplastic composition which has been found to besatisfactory is as follows:

'Other suitable materials are: A mixture of gilsonlte selectswith softasphalt; chlorinated paraffin; ceresin wax: a mixtureof rosin andrubber; and a, mixture of stearlc acid, tallow, l

candelilla wax and petrolatum.

For a typical flashlight dry cell 11,/4 inches diameter by 2% incheshigh.v a thermoplastic disc one-sixteenth inch thick and seven-eighthsinch in diameter 'with acenter hole eleven thirty-sec- ;onds inch indian'i'eter is satisfactory for disc D.

Various means, such as an open flame, electrical heating as by'induction or high frequency,

-above theheater H. An exposure of about r0r exposure to radiantheat,may be used to apply heat to the closure or to the top part'of the cellto melt the internal thermoplastic disc. As

shown in Fig. 3. vradiant heat preferablyl is used and may be applied byan electrically heated body H consisting of al ribbon of metalresistance alloy such as nichrome. A suitable spacingmember H' maysupport the cell at the proper distance secondaxat a distance of aboutone-fourth inch between the' cover of the cell and the radiant body Hheated to about .cherry has .been

found satisfactory to melt a properly located disc -of the'type of discD. Obviously. the vheating interval twill vary'with various factors suchas theA nature of the thermoplastic 'materiaILthe temperature ofthecell. the type of closure, etc,`

`The use ofwthe thermoplastic material in-ring or disc form affordsdistinct advantages 'in"han dlinz andin :controlling the quantity anddistribution 'ofjrateriaL However, in ysome .in-

' stances. e. e.. for less precise distributionof the protective mass.thermoplastic material in loose,

freely-movable pul'verized or pellet form may be placed on lthe collar Kin the cell.A Such pellet material R is shown in the inverted cell ofFigure 8, ready to be heated as previously described to produce arelatively thick solid, adherent prof teetive mass similar to the massP'of Figure l.

The procedure illustrated in Figure 9 has also j been found practicable.Herea molten sealing material S of Athe kind already described is pouredonto the collar K justprlor to: the seamo ing or closing operatiom Theclosure is then quicklv Spun 'in place: and the cell is quicklyinverted. .The molten material then flows down y sind colmiletely coversthe interior surfaces lto bel 1:u'otec ted and.upon cooling toi-oomtempera- .turc .so1idiesand-.produces a solid adherent 'tastimass-similar" tothe rotective mass of 've p' which saidmassoi'majrial'internally covers the latter. 4For example, in'applyingthe mass P" the localized heating maybe-concentrated upon the outer seamor` `joint o f the closure and the In some instances, instead of using athermo.

plastic material it. is desirable to use materials which will polymerizeto produce the desired adherent coating or protective mass. As shown inFigure 10, a suitable polymerizable material T may be deposited orpoured onto the collar K just prior to the closing operation. After theclosurehas been permanently secured in place, the celiis inverted andaged in the inverted position until the polymerizing material hassolidiiledvto -pro duce a protective mass similar to the coating ormassPofFigure l. llnrthispm'poseithasbeen found satisfactory to use atung oil which is poly'meriz'ed by ferric chloridef-a practical formulabeing: Tung oil, 100 grams; ferric chloride, 6 grams: and acetone, 2grams. If the materials which form the protective mass react tooquickly, they may be kept separate until after the cell has been closedand inverted. This may be done by f l sacrificing its advantages. 'i

What is claimed is: l. A galvanic cell comprising a container'electmde;aninner electrode'therein; a metal closure solidified mass ofthermoplastic m isturerepely lent material permanently adhering tovandcoveringat least a portion ofthe interior'surface of said closure andthe adjoining interior surface portion of one of said electrodes andalso bridging and internally covering the joint between said closure andsuchy adjoining electrode portion, said unitary mass being electricallynon-conductive and constituting the sole means for intere ingI onemargin thereof rigidly secured to said container electrode; electrolytematerial within..

said container electrode between the latter and the said electrodevmember, leaving a free space said electrolytematerial; a metal capcarried by said electrode member having `a portion cap: andarelativelythicksolidified mass consisting' solely of thermoplastic protectivematerial permanently adhering tolsaid closure member and to the metalcap ,within said ,free space an'd covering the joint between saidclosure member and said cap, said relatively thick rassof v:materialresisting creepage of said electrolyte to Said joint.'

s. A gaivanic een as l-aimed in claim'l, m

- which vsaid ms of material internally covers the `ioint'between saidcontainer electrode and said closure.

eruit; surface within'v said free space; une said .closure member alsohaving 'a marginal portion supported by but electrically insulated fromsaid,

joint between said inner electrode and said closure.

5. A.galvanic cell as claimed in claim l, in which said mass of materialinternally covers the joints between said closure and said electrodesand also completely covers the interior surface of said closure. 4.

6. A galvanic cell as claimed in claim 1, in which said closurecomprises a metal cap carried by said inner electrode, and a metal covermember having a marginal portion bearing against but electricallyinsulated from said cap; and said mass of material bridges and coversthe internal portion of the joint between said cap and said covermember.

7. A gaivanic cell comprising a container electrode; an inner electrodetherein; a metal cap carried by said inner electrode and having a ange;an insulating washer' seated on said flange; an annular metal coverhaving its outer margin permanently secured to said container electrodeand its inner margin engaging said washer; and a relatively thicksolidified mass consisting solely of thermoplastic moisture-repellentand electrically non-conductive material permanently adhering to andcovering the interior surfaces of said flange and said cover and lcover.

' 8. A dry cell comprising a zinc container electrode; a carbonelectrode centrally therein; active-` material, including a4deliquescent saltin said container electrode between said electrodes; aclosure for said cell comprising a metal cap tting the top end of saidcarbon electrode and having a iiange, a washer of electrical insulatingmaterial seated on said flange, and an annular sheet metal cover havingits outer margin permanently secured to the top end of said containerelectrode and having its inner margin engaging said Washer; and arelatively thick and solid mass consisting solely of thermoplasticmoisture-repellent and electrically non-conductive material permanentlyfused into position against and adhering to the interior surface of saidclosure and in-A ternally covering the joints between said closure andsaid electrodes. A

9. A galvanic cell comprising a container electrode; an inner electrodetherein; a cell closure having a portion supported by said innerelectrode and an outer margin interlocked with, and thereby permanentlysecured to, a portion of said container electrode, to permanently unitesaid closure to said container electrode; and a unitary relatively thicksolidified mass of thermoplastic moisture-repellent material permanentlyadhering to and covering atleast a portion of the interior surface ofsaid closure and the adjoining interior surface portion of one of saidelec-v trodes` and also-bridging and internally covering th'e jointbetween said closure and such adjoinand across said joint.

PAUL A. MARSAL.

